1. Field of the Invention
The present invention relates to an apparatus for improving the reception sensitivity of a public wave receiver, and more particularly, to an apparatus for improving reception sensitivity of a public wave receiver by reducing noise externally-emitted in the public wave receiver, which generates serious noise due to switching operations of power devices built in a power supply of the receiver.
2. Brief Description of the Background Art
Recently, electronic digital products include special power supplies for stable and reliable supply of power. The power supply uses chip-type power devices for stably supplying power by switching operations in order to decrease the size and weight of the power supply.
An SMPS (Switched Mode Power Supply) can also be employed as the power supply.
FIG. 1 is a plan view illustrating the power supply where general power devices are mounted on a substrate, and FIG. 2 is a side view illustrating the power supply.
Referring to FIGS. 1 and 2, the power supply includes a substrate 1 on which various elements are mounted including power devices 3 for performing switching operations, and leads 4 extending from the side portions of the power devices 3 for mounting the power devices 3 on the substrate 1.
In order to stably supply power through the power supply, the power devices 3 perform the switching operations.
Switching noise is externally emitted due to the switching operations of the power devices 3, which influences the other components of an electronic apparatus main body on which the power supply is installed.
The emitted noise seriously generates failures in public wave reception of a public wave receiver. For example, the public wave receiver mistakenly recognizes a frequency interrupted by the emitted noise as the normal one during the AM/FM signal search. This is referred to as a noise stop phenomenon.
In addition, a switching frequency and/or multiplied frequency of the power devices 3 is transmitted to an antenna through an antenna connecting line, mingled with a reception frequency band, and operated as noise. It is thus impossible to receive normal public waves in a desired frequency band, which reduces reception sensitivity and generates noise.
FIG. 3 is a perspective view illustrating an antenna of the general public wave receiver.
As illustrated in FIG. 3, the antenna includes an antenna frame 5 generally formed in a rectangular shape, a wire winding unit forming the outer circumference of the antenna frame 5, and a wire 6 wound around the wire winding unit multiple times.
The antenna further includes a connecting wire 7 with one side connected to the wire 6 and the other side connected to a public wave receiver main body. The connecting wire 7 serves to transmit public wave signals from the wire 6 to the public wave receiver main body. The connecting wire 7 has a signal line 8 for transmitting the signals and a ground line 9 for grounding, which are separately formed and twisted with each other.
The antenna of the general public wave receiver is connected to the public wave receiver main body through the connecting wire 7, and the antenna frame 5 is properly positioned for public wave reception.
However, the switching frequency and/or multiplied frequency generated by the power devices (3 of FIG. 1) is mingled with the frequency band which the antenna intends to receive, and produces noise. Therefore, public wave reception of a wanted frequency band is not performed, or reception sensitivity thereof is reduced.
For example, the power devices 3 may have a switching frequency of 375 KHz in the public wave receiver receiving AM signals whose frequency band ranges from 540 to 1600 KHz. Here, the switching frequency generated by the power devices 3 is transmitted to the connecting wire 7 of the antenna, and thus produces noise in the AM signals received by the pubic wave receiver. As a result, normal frequency reception is impossible.
Moreover, the signal line 8 and the ground line 9 of the connecting wire 7 are twisted with each other, which is not attractive. In addition, the whole shape of the connecting wire 7 may be deformed due to an untwisting force of the twisted signal line 8 and ground line 9.